Robert F. Kennedy Jr. has continued to broadly advise Trump and the transition team on health-related appointments and has been in discussions to possibly fill a major role in the next administration, sources familiar with the matter told ABC News.

While sources caution that a role has not been finalized, RFK Jr. has been discussed as a potential candidate for the next secretary of Health and Human Services. But other roles are also on the table, including a broad "czar"-like position that would advise on policy and personnel decisions in other health arenas, the sources said.

RFK Jr. has been in active discussions with the transition team since Trump's election victory last week. He's been spotted at Trump's Mar-a-Lago club multiple times and has been engaging in presentations which include candidates for specific Cabinet and health-related jobs, sources said.

He has spent hours with the co-heads of Trump's transition team -- billionaire Howard Lutnick and Linda McMahon -- in addition to others at Mar-a-Lago such as Trump's son Donald Trump Jr.; investor and donor Omeed Malik; Tucker Carlson; and Del Bigtree, RFK Jr.'s former campaign spokesperson who produced a documentary called "Vaxxed: From Cover-Up to Catastrophe."

-ABC News' Katherine Faulders, Olivia Rubin and Will McDuffie

President-elect Donald Trump has tapped former New York Rep. Lee Zeldin to lead the Environmental Protection Agency.

"Lee, with a very strong legal background, has been a true fighter for America First policies," Trump said in a statement. "He will ensure fair and swift deregulatory decisions that will be enacted in a way to unleash the power of American businesses, while at the same time maintaining the highest environmental standards, including the cleanest air and water on the planet. He will set new standards on environmental review and maintenance, that will allow the United States to grow in a healthy and well-structured way."

Zeldin, who also ran for New York governor against Andrew Cuomo in 2022, confirmed he had been offered the job via a post on X.

"It is an honor to join President Trump’s Cabinet as EPA Administrator," he wrote. "We will restore US energy dominance, revitalize our auto industry to bring back American jobs, and make the US the global leader of AI. We will do so while protecting access to clean air and water."

-ABC News' John Santucci, Rachel Scott and Katherine Faulders

Robert F. Kennedy Jr. indicated over the weekend that he would fire 600 employees at the National Institutes of Health, replacing them with a new cohort of workers as he seeks to dramatically reshape America's health agencies.

Speaking at the Genius Network Annual Event in Scottsdale, Arizona, Kennedy described his role vetting people for Donald Trump's new administration.

"We need to act fast, and we want to have those people in place on Jan. 20, so that on Jan. 21, 600 people are going to walk into offices at NIH and 600 people are going to leave," Kennedy said, according to a video of his remarks posted on YouTube.

-ABC News' Will McDuffie